AuthorTopic: FAQ: Octane Analysis (Read 68455 times)

IrvineHad they had the additional 40 gallons on board when they landed at Gardiner then , for only one engine at battery charging rpms, it would have represented perhaps 5 hours of additional radio time. Provided of course that the plane didn't get washed into the sea before then.

As I said before, Gas left behind on a truck at the airfield is of absolutely no use whatsoever and ya never know when ya might need it.

I have seen that phrase from several people in these forums. Would you say this is a common practice to always fill every tank at every opportunity? Is it an old practice going back to the 30's as such? Would she have been asked at Lae if she wanted the 100 octane tank topped up and refused? I ask because I believe that there is a reason she didn't fill it.

I agree with everyone that having the extra fuel would be smart. Your point of being able to run the engine for extra radio time is a very valid. But when someone doesn't do the expected or the norm it makes me question why they did that. Or was the norm of the day to believe that 100 octane would boost take off power. There is a reason she did what did. Poor judgement, mis informed, maybe nobody bothered to fill that tank? What's the likeliest reason? Does it effect the hypothesis?

AE had no idea whether she would need those 40 gallons, she had no idea that she would be on an island radioing for help, athat's my point. Ya never know when ya might need it, so take it along just in case.

I don't know what was common practice in the '30's or even in the 70's when I was first flying. I only know what my instructor taught me, it made sense to me, and it became a habit and part of my pre-flight practice when preparing for a cross-country.

I also got into the habit of performing a complete walk around pre-flight of the plane prior to taxi, regardless of how long or how little time I was away from the plane. Habit.

Seems AE should have had your instructor. I have several boater friends who enjoy the northern parts of the great lakes. It's common for them to top up whenever they can too. You just never know when you need that little extra mileage. So I am leaning towards AE being too nonchalant in her planning. Even if she believed the notion that 100 octane helped boost take offs or not, she should have made sure she had 100 octane available for top up at every stop. As Jeff Neville points out, she had 200 gallons being delivered by Itasca for top up at Howland. Ric reminds us that she had fuel propositioned in drums at her stops. Why not a 100 octane top up at Lae regardless of the reason she was carrying it? You're right Harry. Seems like perhaps she just didn't have the habit.

I have seen that phrase from several people in these forums. Would you say this is a common practice to always fill every tank at every opportunity? Is it an old practice going back to the 30's as such? e hypothesis?

Running out of fuel in flight is a bigger deal than running out while driving your car. Because of this, pilots are trained to be conservative about their fuel supply. There is another reason to fill the tanks up that Harry hasn't mentioned. Fuel gauges in airplanes are notoriously inaccurate today and they were no better 74 years ago. The only way you can be certain of how much fuel you have is when the tanks are full. Federal regulations (posted below) requires that the fuel gauge only be accurate at one point, it must read "zero"at the level of "unusable fuel" which is fuel remaining in the tanks that might not be usable in extreme flight attitudes. Most of the time you can use the "unusable fuel" in normal flight attitudes. Another way to look at the regulation is that the engine can not run out of fuel prior to the gauge indicating "zero" but the engine may continue to run after that point in normal flight attitudesSome aircraft fuel gauges are marked simply "0" which also has a "RED LINE"; 1/4; 1/2; 3/4 and "F". Others have markings in gallons. Pilots know to take these markings with a grain of salt since there is no regulation setting out a required accuracy for these marks, except for the RED LINE, and they are not very accurate.

It is difficult to make accurate fuel gauges for airplanes due to the shape of the fuel tanks in the wings, they are long and wide but very shallow, limited by the thickness of the wing. This means that the float on the sending unit has a very limited range of movement that is picked off by a rheostat which is coarse and the wiper may stick between windings. Also, most wings have dihedral meaning that the wing tips are above the wing roots making accurate readout of the fuel even more difficult. In turbulence and when the airplane is maneuvering the fuel can slosh back and forth in the long shallow tanks making the fuel gauges move up and down as the fuel moves around.

Pilots know that they can't rely on their fuel gauges so the most accurate and reliable way to determine the fuel on board is to fill up the fuel tank. Unless there is a major concern with exceeding the maximum gross weight limit, pilots will fill their tanks completely before takeoff. Because of the many separate fuel tanks in the fuselage Earhart could be very confident with their knowledge of the fuel remaining as each tank was drained one by one. After all the fuselage fuel was consumed they only had the inaccurate fuel gauges to rely on in measuring the fuel remaining in the wing tanks.

Since pilots can't rely on their fuel gauges they rely on their clocks. The operating manual tells you what your rate of consumption is at various power setting and altitudes and you divide the amount of fuel in the full tank by the rate of consumption to compute your endurance. If you have multiple tanks you can time how long each lasts and compute your actual rate of consumption which should be a bit more accurate than relying on the aircraft manual and I would expect that Earhart or Noonan did this as each of the fuselage tanks were emptied. But this consumption rate is only valid if the power setting and altitude and temperature remain constant and it is likely that Earhart reduced power as the plane got lighter so their calculated fuel consumption rate could have been inaccurate towards the end.------------------------------------------Federal Aviation Regulations, 14 CFR -

§ 23.1553 Fuel quantity indicator.

A red radial line must be marked on each indicator at the calibrated zero reading, as specified in §23.1337(b)(1).

§ 23.1337 Powerplant instruments installation.......

(b) Fuel quantity indication. There must be a means to indicate to the flightcrew members the quantity of usable fuel in each tank during flight. An indicator calibrated in appropriate units and clearly marked to indicate those units must be used. In addition:

(1) Each fuel quantity indicator must be calibrated to read "zero" during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply determined under §23.959(a);

§23.959 Unusable fuel supply.

(a) The unusable fuel supply for each tank must be established as not less than that quantity at which the first evidence of malfunctioning occurs under the most adverse fuel feed condition occurring under each intended operation and flight maneuver involving that tank. Fuel system component failures need not be considered.

But the TIGHAR hypothesis is that they landed on Gardner with fuel on board. IF they had filled that last tank at Lae, wouldn't this just mean they would have had more fuel in the tank when they landed? It's not like AE flew around until her tanks went empty then crashed into the sea. The post loss radio messages say otherwise.

Yes, if you accept TIGHAR' hypothesis, which you may have noticed, I don't.

Is there a record of her asking what shape the new unpaved strip was in?

Since we now know that the Coast Guard landed two drums of 100 octane, this issue is moot, but to make this inquiry complete I have attached a radiogram from Itasca to Earhart dated June 25, 1937 showing the lengths of the runways at Howland, the longest being 4100 feet.

Thanks Gary for that explanation on gas gauges and fuel tanks. Very clear explanation for non aviators like myself.

Regarding the radiogram to AE, do we know that she received it? Do we know if it affected her decisions in regards to preparations to leave Lae?

As a non aviator perhaps you could also clarify for me which of the runways she was "likely" to use for take off. Were there three? They mention 4100 ft, 2600 ft and 2250 ft. They also note prevailing winds out of the east and adding 300 ft to one of the runways to give it a total of 2750 ft. However adding 300 ft to any of the runway lengths listed doesn't give any of them a total of 2750 ft. And the radiogram says 300 feet is "being added", not "have" added or "will have added by the time you arrive". What am I missing?

Thanks Gary for that explanation on gas gauges and fuel tanks. Very clear explanation for non aviators like myself.

Regarding the radiogram to AE, do we know that she received it? Do we know if it affected her decisions in regards to preparations to leave Lae?

As a non aviator perhaps you could also clarify for me which of the runways she was "likely" to use for take off. Were there three? They mention 4100 ft, 2600 ft and 2250 ft. They also note prevailing winds out of the east and adding 300 ft to one of the runways to give it a total of 2750 ft. However adding 300 ft to any of the runway lengths listed doesn't give any of them a total of 2750 ft. And the radiogram says 300 feet is "being added", not "have" added or "will have added by the time you arrive". What am I missing?

The takeoff speed of the plane at 16,500 pounds without the use of flaps was 104 mph and with 30° flaps it was 95 mph. The two computed takeoff distances at sea level and no wind are 2,600 and 2,100 feet, respectively. A headwind on takeoff shortens the takeoff distance because the airplane only has to accelerate to a lower ground speed in order to reach flying speed. Using the Electra as an example, it can take off at 95 mph. If it lines up on the runway facing a 20 mph headwind then there is already 20 mph of air going over the wings so the plane will only have to accelerate an additional 75 mph in order to take off. This takes fewer seconds and the seconds that are saved would have been seconds near the end of the takeoff when the plane would be moving fast. This 21% of takeoff speed wind would result in a 38% reduction of takeoff distance so the plane could take off in only 1302 feet into a 20 mph wind. A 10 mph wind would result in a 20% reduction allowing a takeoff in only 1680 feet. If there is no wind then you use the longest runway, 4100 feet on Howland. If there is a strong enough cross-wind to make airplane control on the takeoff roll difficult then the strong wind will allow a takeoff on the shorter runway that faces into the wind. We also know that the plane would be a lot lighter on takeoff at Howland so would have a shorter takeoff distance, see:https://tighar.org/smf/index.php/topic,528.msg7061.html#msg7061

In my prior post I wrote, "I'll leave you with just one word, PLANK. ," I was just being humorous and I fully expected that you would recognize the standard aircraft engine thermodynamic formula for computing horsepower by the use of "PLANK." Since you didn't even recognize this standard formula, I now take it that you never learned how to compute horsepower and this probably explains your misunderstanding of the power settings contained in the P&W TCDS E-143 and in the P&W power setting table for the S3H1 engine. I thought that this formula was taught to all A&Ps (you are an Airplane and Powerplant Mechanic, right) so did you miss class that day, or what?I have attached the FAA test questions for the A&P General Exam, try questions 34, 36, 37, 38, 44 and 57 as a review.As long as we are at it Jeff, since you also post about Noonan's navigation, I have attached the FAA Flight Navigator test questions, let me know how you do on them.

gl

Gary,

No, I didn't miss school that day. Did you miss moot court? Something's left wanting here...

I had referred to a gentleman who happened to be a 'plank owner' and made the mistake of thinking somehow you'd picked-up on that - he happened to have been an original Hurricane Hunter and taught me much in my career. Sorry, oddly enough I thought you were complimenting the gentleman's navy career and inferring something about your own. Yes, he was a 'PLANK'. That's a small stage.

You "take it" wrongly in deciding by that that I do not 'know' the formulae, etc. by my simply missing your 'meaning'. Conclude as you will, but no, I didn't miss class 'that day' and in fact got sterling marks for mastering that (power calculations for application in cert data, practical applications etc.) and many other formulae - in A&P school and later in Engineering school. I just didn't think of the 'handy-dandy-ditty' you are apparently accustomed to throwing about on this occasion.

I also have no problem well understanding the data in the TCDS E-143 - and find it tiring that you continue to try to impeach all who disagree with you as a matter of course. Actually you could use a 'brush up' with applying that data -

You should have recognized the effects of boost (via supercharger) on the Wasp long ago but in all I've seen you point out you've focused almost solely on HP numbers and never seemed to grasp the effects of intake pressure and what effect it has on... the 'thermodynamic' model for one... and how that model would be applied to what goes on in a 'low compression' engine like NR16020 had. You seem to have sailed right past all the facts of 'mass' as a function in the equation. Physician, heal thyself - your practical grasp could use some polish. Meanwhile I think I'll just hang on to my appendix...

Thanks for the 'nav challenge' - I'm sure I'll enjoy the new exercise when I find the time.

And once again we have a thread that has tortured itself into the weeds and far beyond much of anything useful to the search at-hand. I should be a better man and just ignore it I guess.

LTM -

-------------------------I'm glad you took my little "ribbing" as intended. I appreciate our exchanges.

Besides, as suggested before - it is getting knuckle-headed for us to clutter up this string with the administrivia of dicephering Rev. 4 of this TCDS from 1973 - published at least 4 iterations and 36 years after AE's particular Wasps disappeared... and with no particular gain to the topic that I can see...

I tried to get the original TCDS and power setting chart from my contacts at P&W and I received this response today:-----------------------------------------------

We have done a quick search (no data base exists for such ancient stuff) to see whether we could locate a copy of the original type certificate E-143 for the Wasp S3H1 (Military R-1340) but were unable to find any. The originals are and always were with Pratt & Whitney in Hartford, Connecticut. You could perhaps contact them or better still the FAA.

P&WC had (probably still valid today) Canadian Department of Transport Type Certificate E3 for the Wasp S3H1 model engine as well as a number of other Pratt & Whitney radial engine models.

P&W Hartford ceased radial engine manufacture in the mid to late 1950’s and transferred production to P&WC (Canadian Pratt & Whitney Aircraft Co. Ltd. as we

were called at that time).

As far as the power setting chart for the Wasp S3H1 we are sure that it could be found in one of the relevant manuals which are buried somewhere in the archives and would require quite a search.

Sorry but this is the best we can do without a lot of digging but if there is anything else let us know and we will try to help if we can.

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